<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
    </ul>
    <ul id='nav'>
        <li>6</li>
        <li>7</li>
        <li>8</li>
        <li>9</li>
        <li>10</li>
    </ul>
    <script>
        // 1. 获取过来元素对象的集合 以伪数组的形式存储
        var lis = document.getElementsByTagName('li');
        console.log(lis);
        console.log(lis[0]);
        // 2. 遍历元素对象
        for (var i = 0; i < lis.length; i++) {
            console.log(lis[i]);
        }

        // 3. element.getElementsByTagName() 可以得到这个元素的某些标签
        var nav = document.getElementById('nav');
        var varLis = nav.getElementsByTagName('li');
        console.log(varLis);
    </script>
</body>

</html>